Outstanding maneuverability and turnability, based on comparatively large steering angles and small turning radii, have helped to establish pivot steering as a type of steering in vehicles with at least two vehicle frames each having at least one rigid axle. In particular construction vehicles, such as for example vibratory rollers with two vehicle frames in each of which a tire is mounted, are often controlled with the aid of pivot steering.
Conventional pivot-steered vehicles frequently use a central pivot joint which connects the two vehicle frames on the axis of symmetry in the longitudinal direction, that is to say the longitudinal centre axis. The steering drive used is in this case usually a double-acting hydraulic cylinder which is articulated at its ends to the two vehicle frames. Depending on the desired change in the direction of travel, the piston rod of the hydraulic cylinder is extended or retracted by actuation of a pressure medium so that, viewed in the direction of travel, either the left or the right lateral edges of the vehicle frames are swiveled relative to one another.
The maximum settable pivot or steering angle of a central pivot joint of this type results from the geometrical context. The smaller the spacing between the front frame and the rear frame becomes, the smaller the maximum settable steering angle becomes, as otherwise the edges of the vehicle frames will abut one another. If a larger steering angle is striven for in order to improve maneuverability, this inevitably increases the size of the free space between the frame edges in which the pivot joint is located, giving rise to a broad range of drawbacks. On the one hand, the total length of the vehicle is increased in size; this can present difficulties during transportation, etc. Furthermore, the increase in the size of the free space between the frame edges in the longitudinal direction increases the axial spacing, as a result of which the size of the turning radius is increased while the steering turn remains the same. Furthermore, the increase in the size of the spacing between the vehicle frames is also associated with increased consumption of materials. Alternatively, in order to increase the steering turn, instead of increasing the size of the spacing between the vehicle frames, the critical frame outer edge regions, in particular corner regions, which delimit the steering turn by abutment, can be recessed and provided with a radius. Although this does not increase the size of the overall length, the recessed regions are nevertheless lost, so that the space in or on the vehicle frames for arranging machine components is reduced.
In relatively small construction machines, such as for example trench rollers, an overall length which is as short as possible is striven for, wherein there must still be sufficient space for arranging machine components. At the same time, it is necessary for the trench roller to be able to perform a steering angle which is as large as possible in order to be able to turn even in narrow and curvy trenches.
A pivot-steered agricultural vehicle with two swivel axes spaced apart from one another is known. A disadvantage of the principle applied in the pivot steering of this vehicle is that the adjustment apparatus for steering the vehicle necessarily entails a relatively large amount of construction room in the longitudinal direction of the vehicle. It is also disadvantageous that a separate adjustment device, for example a hydraulic cylinder, is required for creating a pivoting movement about each swivel axis, which increases the cost and decreases the effectiveness of the steering apparatus.